利用噴霧氣流降低高溫室內溫度之研究

Abstract

本文主要目的為利用數值計算，研究推進器在排氣管中測試而衍生的相關熱流問題。推進器在測試時，將產生大量高溫廢氣，嚴重影響鄰近人員安全，欲解決上述問題需仰賴有效的降溫排氣系統方足以勝任。將高溫氣體降溫主要有兩種方法，一種是吸入外界冷空氣，另一種則是利用噴霧氣流。 在數值計算流場方面採用k-e紊流模式，利用有限體積法求得降溫排氣管之流場與溫度場分佈。結果顯示空氣導入管距噴口越近，會引進更多的冷空氣，使排氣系統降溫較多，但排氣結構的受力也相對較大。噴霧氣流水量越大，也會使廢氣排出口溫度越低，且在一定範圍之水滴直徑大小對出口溫度的影響不甚明顯，但再小的水滴，會帶走更多的熱量，使排氣出口溫度越低。

The main purpose of this study is to solve thermal and flowing structure induced by a jet in exhaust region. The characteristics of flow and thermal fields are analyzed with numerical method. Generally, a jet produces huge amount of high temperature and hazardous exhausted gas which seriously damage people around neighborhood. To solve this problem, we need an exhaust structure which can effectively lower the temperature. There are two kinds of ways to lower temperature. One is naturally induce cold air into the exhaust region surrounded by a intake, the other way is using liquid sprays. In this numerical analysis, the finite volume method is coupled with turbulent model to find out the flow and thermal structure. The numerical results show that the shorter the horizontal distance from jet to the intake, the more cold air is induced, however the bigger overall stress is sustained by the duct. Larger amounts of liquid sprays shows that more heat is taken, thus the low temperature at outlet.